Dielectric filter and method for manufacturing the same

ABSTRACT

The invention relates to a method of manufacturing a dielectric filter. The method comprises the steps of: (a) preparing a ceramic substrate; (b) applying a conductive paste on the ceramic substrate, wherein the conductive paste comprises, (i) 100 parts by weight of a conductive powder, (ii) 0.1 to 10.0 parts by weight of a glass frit comprising silicon oxide, boron oxide, aluminum oxide and an alkaline metal oxide, and (iii) an organic vehicle; and (c) firing the applied conductive paste.

FIELD OF INVENTION

The present invention relates to an electrical component, particularlyto an electrode on a ceramic substrate and an electrical componentcomprising thereof. More particularly, the present invention relates todielectric filter suitable for radio frequency.

TECHNICAL BACKGROUND OF THE INVENTION

An electrode on a ceramic substrate of dielectric filter needs tocontribute to better performance of the electrical component.

WO2009006242 discloses a conductive paste for a ceramic substrate ofalumina or aluminum nitride. The conductive paste comprises a) aconductive metal powder comprising silver and palladium, b) aBi₂O₃—SiO₂—B₂O₃ glass powder and c) an organic solvent, wherein theconductive metal powder has an average particle diameter of not morethan 1.2 μm.

EP2940783 disclose a transverse electromagnetic (TEM) mode dielectricfilter, wherein the TEM mode dielectric filter comprises a dielectricbody and a silver plating layer, wherein the silver plating layer coversa surface of the dielectric body, and a dielectric constant of thedielectric body is less than or equal to 21.

SUMMARY OF THE INVENTION

An objective is to provide a dielectric filter having a betterperformance.

An aspect relates to a method of manufacturing a dielectric filter,comprising the steps of: (a) preparing a ceramic substrate; (b) applyinga conductive paste on the ceramic substrate, wherein the conductivepaste comprises, (i) 100 parts by weight of a conductive powder, (ii)0.1 to 10.0 parts by weight of a glass frit comprising silicon oxide,boron oxide, aluminum oxide and an alkaline metal oxide, and (iii) anorganic vehicle; and (c) firing the applied conductive paste.

Another aspect relates to a conductive paste to form an electrode ofdielectric filter, wherein the conductive paste comprises: (i) 100 partsby weight of a conductive powder, (ii) 0.1 to 10.0 parts by weight of aglass frit comprising silicon oxide, boron oxide, aluminum oxide and analkaline metal oxide, and (iii) an organic vehicle.

Another aspect relates to dielectric filter comprising a ceramicsubstrate and an electrode on the ceramic substrate, the electrodecomprises (i) 100 parts by weight of a conductive powder, and (ii) 0.1to 10.0 parts by weight of a glass frit comprising silicon oxide, boronoxide, aluminum oxide and an alkaline metal oxide.

Dielectric filters of the present invention have better performance suchas Q value.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 depicts one embodiment of a ceramic substrate;

FIG. 2 depicts one embodiment of a resonator; and

FIG. 3 depicts one embodiment of a filter.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The method of manufacturing an electrode comprising the steps of: (a)preparing a ceramic substrate, (b) applying a conductive paste on theceramic substrate, and (c) firing the applied conductive paste.

The ceramic substrate has a dielectric constant, ε_(γ), of 9 to 50 in anembodiment. The ceramic substrate contains a dielectric constant of 15to 45 in an embodiment, and 20 to 40 in another embodiment. Dielectricconstant of the ceramic substrate can be measured by a known method orby a commercial measurement equipment. In an embodiment, dielectricconstant is measured by the method of ASTM Standard D2520 at 5 GHz. Suchceramic substrates are suitable for ceramic filters used in radiofrequency. More specifically, the ceramic substrates are suitable forceramic filters used in 1 GHz to 10 GHz.

Ceramic substrate compositions are described herein as including certainmetal oxide components. Specifically, the metal oxide components are thecomponents used as the starting material that is subsequently processedto form a ceramic substrate. Such nomenclature is conventional to one ofskill in the art. As recognized by one of ordinary skill in the art inceramic chemistry, a certain portion of oxygen may be released duringthe process of making the ceramic substrate.

Metal components of the ceramic substrate are selected from the groupconsisting of Al, Ba, Ca, La, Mg, Mn, Nb, Nd, Ni, Pb, Sm, Sn, Sr, Ta,Ti, Zn, Zr and a mixture thereof. 60 mol %, 70 mol %, 80 mol %, 90 mol %or 100 mol % of metal components of the ceramic substrate is composed ofthe above metal or a mixture in an embodiment. In an embodiment, othermetal(s) are included as metal component of the ceramic substrate.

The ceramic substrate include, but not limited to, Al₂O₃ (ε_(γ)=9),BaTi₄O₉ (ε_(γ)=38), Ba₂Ti₉O₂₀ (ε_(γ)=37), BaSnO₃, BaMgO₃, BaTaO₃,BaZnO₃, BaZrO₃, Ba(ZrTi)O₃, Ba(NiTa)O₃, Ba(ZrZnTa)O₃,Ba(Mg_(1/3)Ta_(2/3))O₃ (ε_(γ)=25), Ba(Mg_(1/3)Nb_(2/3))O₃,Ba(Zn_(1/3)Ta_(2/3))O₃ (ε_(γ)=30), Ba(Zn_(1/3)Nb_(2/3))O₃ (ε_(γ)=41),Ba(Mn_(1/3)Ta_(2/3))O₀₃, CaTiO₃, (CaSrBa)ZrO₃, MgTiO₃,(Mg_(0.95)Ca_(0.005))TiO₃ (ε_(γ)=21), SnTiO₄, SrTiO₃, SrZrO₃,Sr(Zn_(1/3)Nb_(2/3))O₃, Sr(Zn_(1/3)Ta_(2/3))O₃, ZrTiO₂,(Zr_(0.8)Sn_(0.2))TiO₄ (ε_(γ)=38), ZrTiO₂ (ε_(γ)=42) and a mixturethereof. In an embodiment, the ceramic substrate is selected from thegroup consisting of Al₂O₃, MgTiO₃, (Mg_(0.95)Ca_(0.05))TiO₃,Ba(Mg_(1/3)Ta_(2/3))O₃, BaTi₄O₉, Ba₂Ti₉O₂₀, Ba(Zn_(1/3)Ta_(2/3))O₃ andBa(Zn_(1/3)Nb_(2/3))O₃, (Zr_(0.8)Sn_(0.2))TiO₄. Any other known ceramicsubstrate or newly developed ceramic substrate may be used.

The ceramic substrate is 500 μm thick or more in another embodiment, 1mm thick or more in another embodiment, 1.8 mm thick or more in anotherembodiment. The ceramic substrate is 100 mm thick or less in anembodiment, 60 mm thick or less in another embodiment, 45 mm thick orless in another embodiment, 20 mm thick or less in another embodiment,12 mm thick or less in another embodiment, 7 mm thick or less in anotherembodiment.

Surface treatment is applied for the ceramic substrate in an embodiment.A smoothing treatment or a roughening treatment is applied on thesurface of the substrate in an embodiment. A primer layer is formed onthe surface of the ceramic substrate in an embodiment. The primer layeris formed by chemical vapor deposition in an embodiment. The primerlayer is formed by plating in another embodiment.

The ceramic substrate is TEM (transverse electromagnetic) modedielectric filter in an embodiment. High Q value rendered by theconductive paste is more effective in TEM mode dielectric filter. Theceramic substrate is TM (transverse magnetic) mode dielectric filter inanother embodiment.

A conductive paste is applied on the ceramic substrate. The conductivepaste is applied by screen-printing, spraying or dipping in anembodiment. The conductive paste is applied by screen-printing inanother embodiment. The conductive paste is applied by spraying inanother embodiment. The conductive paste is applied by dipping theceramic substrate into the conductive paste in another embodiment.

The conductive paste is applied on the entire surface of the ceramicsubstrate in an embodiment. In case of TEM (transverse electromagnetic)mode dielectric filter, the entire surface of the ceramic substrate iscovered with the conductive layer made from the conductive paste in anembodiment, at least 90%, 95%, 98% or 99% of the ceramic substrate iscovered with the conductive layer in an embodiment.

The conductive paste viscosity can be adjusted to be suitable for theapplying method such as screen-printing, spraying or dipping. Viscosityof the conductive paste is 0.5 to 550 Pa-s in an embodiment, 1 to 500Pa-s in another embodiment, 5 to 450 Pa-s in another embodiment, 10 to400 Pa-s in another embodiment measured by Brookfield HBT with a spindleSC4-14 at 10 rpm or ½RVT with a spindle RV3 at 10 rpm.

The applied conductive paste is 5 to 40 μm thick in an embodiment, 7 to30 μm thick in an embodiment, 10 to 20 μm thick in another embodiment.

The applied conductive paste is optionally dried before firing step inan embodiment. The drying condition is 50 to 250° C. for 3 to 30 minutesin an embodiment.

The applied conductive paste is fired to become an electrode. The firingpeak temperature is 600 to 1100° C. in an embodiment, 650 to 1050° C. inanother embodiment, 800 to 1000° C. in another embodiment. Firing timeat the peak temperature is 3 to 30 minutes in an embodiment, 5 to 20minutes in another embodiment, 7 to 15 minutes in another embodiment.

The electrical component is used in radio frequency. More specifically,the ceramic substrates are suitable for ceramic filters used in 1 GHz to10 GHz.

One embodiment of a filter is illustrated in FIG. 1 and FIG. 2. Theceramic substrate 101 comprising a hole 105 is prepared (FIG. 1). Anexternal electrode 203 is formed on the outer surface of the ceramicsubstrate (FIG. 2). An internal electrode 207 is formed on the internalwall of the hole 105. The conductive paste is applied by spraying ordipping to form the internal electrode 207 and by spraying, dipping orscreen printing to form the external electrode 203 in an embodiment. Theresonator 200 comprises a ceramic substrate 101 comprising a hole 105and an external electrode 203 on the outer surface of the ceramicsubstrate and an internal electrode 207 on the internal wall of the holein an embodiment.

Typically, multiple resonators are placed to form a dielectric filter.In an embodiment, a single resonator is used as a dielectric filter.Such resonator composed of a single resonator is encompassed asdielectric filter in this specification.

One embodiment of a dielectric filter 300 is illustrated in FIG. 3. Thedielectric filter 300 comprises a ceramic substrate and an externalelectrode 303 on the outer surface of the ceramic substrate. The ceramicsubstrate comprises two holes 305 in an embodiment. Internal electrodes307 are formed inside the internal wall of each hole 305. The dielectricfilter comprises at least one hole in another embodiment. The dielectricfilter 300 comprises a ceramic substrate comprising at least one holeand an external electrode 303 on the outer surface of the ceramicsubstrate and an internal electrode 307 on the internal wall of the hole305 in an embodiment.

The internal electrode is 5 to 40 μm thick in an embodiment, 7 to 30 μmthick in an embodiment, 10 to 20 μm thick in another embodiment.

The external electrode is 5 to 40 μm thick in an embodiment, 7 to 30 μmthick in an embodiment, 10 to 20 μm thick in another embodiment.

The conductive paste to form an electrode is explained hereafter. Theconductive paste comprises, (i) 100 parts by weight of a conductivepowder, (ii) 0.1 to 10 parts by weight of a glass frit and (iii) anorganic vehicle.

(i) Conductive Powder

A conductive powder is a powder to provide the electrode withelectrically conductivity. A conductive powder is a metal powder withelectrical conductivity of 7.00×10⁶ Siemens (S)/m or higher at 293Kelvin in an embodiment, 8.50×10⁶ S/m or higher at 293 Kelvin in anotherembodiment, 1.00×10⁷ S/m or higher at 293 Kelvin in another embodiment,4.00×10⁷ S/m or higher at 293 Kelvin in another embodiment.

The conductive powder can be a metal powder selected from the groupconsisting of aluminum (Al, 3.64×10⁷ S/m), nickel (Ni, 1.45×10⁷ S/m),copper (Cu, 5.81×10⁷ S/m), silver (Ag, 6.17×10⁷ S/m), gold (Au, 4.17×10⁷S/m), molybdenum (Mo, 2.10×10⁷ S/m), magnesium (Mg, 2.30×10⁷ S/m),tungsten (W, 1.82×10⁷ S/m), cobalt (Co, 1.46×10⁷ S/m), zinc (Zn,1.64×10⁷ S/m), platinum (Pt, 9.43×10⁶ S/m), palladium (Pd, 9.5×10⁶ S/m),an alloy thereof and a mixture thereof in an embodiment. The conductivepowder can be selected from the group consisting of silver, gold,copper, an alloy thereof and a mixture thereof in another embodiment.The conductive powder comprises silver in another embodiment. Theconductive powder comprises palladium less than 0.1 wt. % in anembodiment, less than 0.09 wt. % in another embodiment, less than 0.06wt. % in another embodiment, less than 0.03 wt. % in another embodimentbased on the weight of the conductive powder. The conductive powdercomprises no palladium in another embodiment.

Particle diameter (D50) of the conductive powder is 0.01 to 10 μm in anembodiment, 0.1 to 5 μm in another embodiment, 0.2 to 3.1 μm in anotherembodiment, and 0.3 to 1.9 μm in another embodiment. The particlediameter (D50) can be measured by laser diffraction scattering methodwith Microtrac model S-3500.

Specific surface area (SA) of the conductive powder is 0.1 to 8 m²/g inan embodiment, 0.3 to 6.9 m²/g in another embodiment and 0.5 to 4.0 m²/gin another embodiment. The specific surface area can be measured by BETmethod with a device Monosorb™ from Quantachrome InstrumentsCorporation.

The conductive powder is 40 to 92 weight percent (wt. %) in anembodiment, 52 to 90 wt. % in another embodiment, 65 to 88 wt. % inanother embodiment, 78 to 86 wt. % in another embodiment, based on theweight of the conductive paste.

(ii) Glass Frit

The glass frit functions to render adhesion of the electrodes to thesubstrate.

The glass frit comprises silicon oxide, boron oxide, aluminum oxide andan alkaline metal oxide.

Silicon oxide is 30 to 85 wt. % in an embodiment, 48 to 83 wt. % inanother embodiment, 52 to 81 wt. % in another embodiment, 57 to 79 wt. %in another embodiment, 60 to 77 wt. % in another embodiment, 62 to 75wt. % in another embodiment, based on the weight of the glass frit.

Boron oxide is 11 to 50 wt. % in an embodiment, 13 to 36 wt. % inanother embodiment, 15 to 34 wt. % in another embodiment, 17 to 31 wt. %in another embodiment, 19 to 29 wt. % in another embodiment, 21 to 27wt. % in another embodiment, based on the weight of the glass frit.

Aluminum oxide is 0.1 to 5.0 wt. % in an embodiment, 0.2 to 4.6 wt. % inanother embodiment, 0.4 to 4.0 wt. % in another embodiment, 0.5 to 3.4wt. % in another embodiment, 0.6 to 2.8 wt. % in another embodiment, 0.7to 2.2 wt. % in another embodiment, 0.8 to 1.8 wt. % in anotherembodiment, based on the weight of the glass frit.

Silicon oxide is SiO₂ in an embodiment. Boron oxide is B₂O₃ in anembodiment. Aluminum oxide is Al₂O₃ an embodiment.

The alkaline metal oxide is 0.5 to 6 wt. % in an embodiment, 0.9 to 5.1wt. % in another embodiment, 1.2 to 4.2 wt. % in another embodiment, 1.4to 3.6 wt. % in another embodiment, 1.6 to 2.9 wt. % in anotherembodiment, 1.8 to 2.2 wt. % in another embodiment, based on the weightof the glass frit.

The alkaline metal oxide is selected from the group consisting oflithium oxide, sodium oxide, potassium oxide and a combination thereofin an embodiment.

Lithium oxide is 0.1 wt. % or more in an embodiment, 0.2 wt. % or morein another embodiment, 0.3 wt. % or more in another embodiment, 0.4 wt.% or more in another embodiment, based on the weight of the glass frit.Lithium oxide is 6.0 wt. % or less in an embodiment, 5.2 wt. % or lessin another embodiment, 4.3 wt. % or less in another embodiment, 3.5 wt.% or less in another embodiment, 2.8 wt. % or less in anotherembodiment, 1.6 wt. % or less in another embodiment, 0.9 wt. % or lessin another embodiment, based on the weight of the glass frit.

Sodium oxide is 0.1 wt. % or more in an embodiment, 0.2 wt. % or more inanother embodiment, 0.3 wt. % or more in another embodiment, 0.4 wt. %or more in another embodiment, based on the weight of the glass frit.Sodium oxide is 6.0 wt. % or less in an embodiment, 5.2 wt. % or less inanother embodiment, 4.3 wt. % or less in another embodiment, 3.5 wt. %or less in another embodiment, 2.8 wt. % or less in another embodiment,1.6 wt. % or less in another embodiment, 0.9 wt. % or less in anotherembodiment, based on the weight of the glass frit.

Potassium oxide is 0.1 wt. % or more in an embodiment, 0.3 wt. % or morein another embodiment, 0.5 wt. % or more in another embodiment, 0.7 wt.% or more in another embodiment, 0.8 wt. % or more in anotherembodiment, based on the weight of the glass frit. Potassium oxide is6.0 wt. % or less in an embodiment, 5.2 wt. % or less in anotherembodiment, 4.6 wt. % or less in another embodiment, 3.8 wt. % or lessin another embodiment, 3.0 wt. % or less in another embodiment, 2.1 wt.% or less in another embodiment, 1.5 wt. % or less in anotherembodiment, based on the weight of the glass frit.

The alkaline metal oxide comprises lithium oxide, sodium oxide andpotassium oxide in another embodiment. Lithium oxide is Li₂O in anembodiment. Sodium oxide is Na₂O in an embodiment. Potassium oxide isK₂O in an embodiment.

The glass frit further comprises an additional metal oxide selected fromthe group consisting of zirconium oxide, titanium oxide, calcium oxide,zinc oxide, magnesium oxide, copper oxide, iron oxide and a combinationthereof in an embodiment. The additional metal oxide is selected fromthe group consisting of zirconium oxide, titanium oxide, zinc oxide,copper oxide, iron oxide and a combination thereof in anotherembodiment.

The additional metal oxide is 0.5 to 20 wt. % in an embodiment, 0.8 to18 wt. % in another embodiment, 1.0 to 15 wt. % in another embodiment,1.5 to 12 wt. % in another embodiment, 1.9 to 10 wt. % in anotherembodiment, 2.2 to 8.5 wt. % in another embodiment, 3.1 to 4.5 wt. % inanother embodiment, based on the weight of the glass frit.

Zirconium oxide is 1.0 wt. % or more in an embodiment, 1.4 wt. % or morein another embodiment, 1.6 wt. % or more in another embodiment, 2.0 wt.% or more in another embodiment, based on the weight of the glass frit.Zirconium oxide is 10 wt. % or less in an embodiment, 8.8 wt. % or lessin another embodiment, 7.9 wt. % or less in another embodiment, 7.1 wt.% or less in another embodiment, 6.2 wt. % or less in anotherembodiment, 4.2 wt. % or less in another embodiment, 3.0 wt. % or lessin another embodiment, based on the weight of the glass frit.

Titanium oxide is 1.0 wt. % or more in an embodiment, 1.8 wt. % or morein another embodiment, 2.6 wt. % or more in another embodiment, 3.5 wt.% or more in another embodiment, based on the weight of the glass frit.Titanium oxide is 15 wt. % or less in an embodiment, 13.8 wt. % or lessin another embodiment, 12.5 wt. % or less in another embodiment, 11.1wt. % or less in another embodiment, 9.5 wt. % or less in anotherembodiment, 8.5 wt. % or less in another embodiment, based on the weightof the glass frit.

Calcium oxide is 1.0 wt. % or more in an embodiment, 1.4 wt. % or morein another embodiment, 1.6 wt. % or more in another embodiment, 2.2 wt.% or more in another embodiment, based on the weight of the glass frit.Calcium oxide is 10 wt. % or less in an embodiment, 8.8 wt. % or less inanother embodiment, 7.9 wt. % or less in another embodiment, 7.1 wt. %or less in another embodiment, 6.2 wt. % or less in another embodiment,4.2 wt. % or less in another embodiment, 3.5 wt. % or less in anotherembodiment, based on the weight of the glass frit.

Zinc oxide is 1.0 wt. % or more in an embodiment, 1.8 wt. % or more inanother embodiment, 2.6 wt. % or more in another embodiment, 3.5 wt. %or more in another embodiment, 5.5 wt. % or more in another embodiment,based on the weight of the glass frit. ZnO is 15 wt. % or less in anembodiment, 13.8 wt. % or less in another embodiment, 12.5 wt. % or lessin another embodiment, 11.1 wt. % or less in another embodiment, 9.5 wt.% or less in another embodiment, 8.5 wt. % or less in anotherembodiment, based on the weight of the glass frit.

Magnesium oxide is 1.0 wt. % or more in an embodiment, 1.4 wt. % or morein another embodiment, 1.6 wt. % or more in another embodiment, 1.8 wt.% or more in another embodiment, based on the weight of the glass frit.Magnesium oxide is 10 wt. % or less in an embodiment, 8.7 wt. % or lessin another embodiment, 6.8 wt. % or less in another embodiment, 5.5 wt.% or less in another embodiment, 4.9 wt. % or less in anotherembodiment, 3.9 wt. % or less in another embodiment, based on the weightof the glass frit.

Copper oxide is 1.0 wt. % or more in an embodiment, 1.8 wt. % or more inanother embodiment, 2.6 wt. % or more in another embodiment, 3.1 wt. %or more in another embodiment, based on the weight of the glass frit.Copper oxide is 10 wt. % or less in an embodiment, 8.2 wt. % or less inanother embodiment, 6.5 wt. % or less in another embodiment, 5.5 wt. %or less in another embodiment, 4.9 wt. % or less in another embodiment,based on the weight of the glass frit.

Iron oxide is 1.0 wt. % or more in an embodiment, 1.8 wt. % or more inanother embodiment, 2.6 wt. % or more in another embodiment, 3.3 wt. %or more in another embodiment, based on the weight of the glass frit.Iron oxide is 10 wt. % or less in an embodiment, 8.2 wt. % or less inanother embodiment, 6.5 wt. % or less in another embodiment, 5.3 wt. %or less in another embodiment, 4.3 wt. % or less in another embodiment,based on the weight of the glass frit.

Zirconium oxide is ZrO₂ in an embodiment. Titanium oxide is TiO₂ in anembodiment. Calcium oxide is CaO in an embodiment. Zinc oxide is ZnO inan embodiment. Magnesium oxide is MgO in an embodiment. Copper oxide isCuO or Cu₂O in an embodiment. Iron oxide is FeO or Fe₂O₃ in anembodiment. The additional metal oxide is selected from the groupconsisting of ZrO₂, TiO₂, ZnO, CuO, Fe₂O₃ and a combination thereof inanother embodiment. The additional metal oxide is selected from thegroup consisting of ZnO, CuO, Fe₂O₃ and a combination thereof in anotherembodiment. The additional metal oxide comprises ZnO in anotherembodiment. The additional metal oxide comprises CuO in anotherembodiment. The additional metal oxide comprises Fe₂O₃ in anotherembodiment.

The glass frit may further comprise bismuth oxide (Bi₂O₃) but not morethan 20 wt. % based on the weight of the glass frit in an embodiment.Bismuth oxide is 15 wt. % or less in another embodiment, 10 wt. % orless in another embodiment, 7 wt. % or less in another embodiment, 3 wt.% or less in another embodiment based on the weight of the glass frit.The glass frit comprises no Bi₂O₃ in another embodiment.

Glass compositions, also termed glass frits, are described herein asincluding percentages of certain components. Specifically, thepercentages are the percentages of the components used in the startingmaterial that was subsequently processed as described herein to form aglass composition. Such nomenclature is conventional to one of skill inthe art. In other words, the composition contains certain components,and the percentages of those components are expressed as a percentage ofthe corresponding oxide form. As recognized by one of ordinary skill inthe art in glass chemistry, a certain portion of oxygen may be releasedduring the process of making the glass.

The softening point of the glass frit is 450 to 900° C. in anembodiment, 550 to 885° C. in another embodiment, 690 to 870° C. inanother embodiment, 730 to 855° C. in another embodiment, 765 to 810° C.in another embodiment.

Particle diameter (D50) of the glass frit is 0.1 to 15 μm in anembodiment, 0.5 to 11 μm in another embodiment, 1.0 to 6.8 μm in anotherembodiment, and 1.5 to 4.5 μm in another embodiment. The particlediameter (D50) can be measured by laser diffraction scattering methodwith Microtrac model S-3500.

The glass frit is 0.1 parts by weight or more in an embodiment, 0.2parts by weight or more in another embodiment, 0.3 parts by weight ormore in another embodiment, 0.4 parts by weight or more in anotherembodiment against 100 parts by weight of the conductive powder. Theglass frit is 10.0 parts by weight or less in an embodiment, 7.5 partsby weight or less in another embodiment, 5.5 parts by weight or less inanother embodiment, 3.9 parts by weight or less in another embodiment,2.7 parts by weight or less in another embodiment, 1.8 parts by weightor less in another embodiment, 0.9 parts by weight or less in anotherembodiment against 100 parts by weight of the conductive powder.

The glass frit is 0.05 wt. % or more in an embodiment, 0.1 wt. % or morein another embodiment, 0.2 wt. % or more in another embodiment based onthe weight of the conductive paste. The glass frit is 5.0 wt. % or lessin an embodiment, 3.8 wt. % or less in another embodiment, 2.5 wt. % orless in another embodiment, 1.0 wt. % or less in another embodimentbased on the weight of the conductive paste.

(iii) Organic Vehicle

The conductive powder and the glass frit are dispersed in an organicvehicle to form a “paste” having suitable viscosity for applying on asubstrate.

The organic vehicle comprises an organic polymer and a solvent in anembodiment. A wide variety of inert viscous materials can be used as anorganic polymer. The organic polymer can be selected from the groupconsisting of ethyl cellulose, ethylhydroxyethyl cellulose, wood rosin,phenolic resin, polymethacrylate of lower alcohol, monobutyl ether ofethylene glycol monoacetate and a mixture thereof. The organic polymeris 0.1 to 50 wt. % in an embodiment, 0.5 to 42 wt. % in anotherembodiment, 1 to 35 wt. % in another embodiment, 2 to 27 wt. % inanother embodiment and 3 to 15 wt. % in another embodiment based on theweight of the organic vehicle.

The solvent can be selected from the group consisting of texanol, esteralcohol, terpineol, kerosene, dibutylphthalate, butyl carbitol, butylcarbitol acetate, dibutyl carbitol, hexylene glycol, dibasic ester and amixture thereof. The solvent is chosen in view of organic polymersolubility. The organic vehicle comprises a mixture of ethyl celluloseand texanol in an embodiment.

The organic vehicle optionally comprises an organic additive. Theorganic additive can be one or more of a thickener, stabilizer,viscosity modifier, surfactant and thixotropic agent in an embodiment.The amount of the organic additive depends on the desiredcharacteristics of the resulting electrically conductive paste.

The organic vehicle is 5 parts by weight or more in an embodiment, 8parts by weight or more in another embodiment, 11 parts by weight ormore in another embodiment, 15 parts by weight or more in anotherembodiment against 100 parts by weight of the conductive powder. Theorganic vehicle is 60 parts by weight or less in an embodiment, 45 partsby weight or less in another embodiment, 39 parts by weight or less inanother embodiment, 31 parts by weight or less in another embodiment, 25parts by weight or less in another embodiment against 100 parts byweight of the conductive powder.

The organic vehicle is 4 to 58 wt. %, 8 to 37 wt. % in anotherembodiment, and 12 to 23 wt. % in another embodiment based on the weightof the conductive paste. The solvent amount can be adjusted to getdesired viscosity of the conductive paste.

(iv) Inorganic Additive

The conductive paste may further comprise an inorganic additive in anembodiment. The inorganic additive could improve adhesion orsolderability. The inorganic additive comprises a metal oxide powderselected from the group consisting of copper oxide (CuO, Cu₂O), ironoxide (FeO, Fe₂O₃), zinc oxide (ZnO), titanium oxide (TiO₂), lithiumruthenate oxide (Li₂RuO₃) and a mixture thereof in an embodiment. Theinorganic additive comprises a metal oxide powder selected from thegroup consisting of copper oxide, iron oxide and a mixture thereof inanother embodiment. The inorganic additive comprises a metal oxidepowder selected from the group consisting of Cu₂O, Fe₂O₃ and a mixturethereof in another embodiment. The inorganic additive comprises amixture of a Cu₂O powder and a Fe₂O₃ powder in another embodiment. Themixing weight ratio of a Cu₂O powder and a Fe₂O₃ powder (Cu₂O:Fe₂O₃) is0.5:1 to 10:1 in an embodiment, 1.1:1 to 8:1 in another embodiment,1.5:1 to 5:1 in another embodiment, 1.8:1 to 3.5:1 in anotherembodiment. The inorganic additive comprises at least a Cu₂O powder inanother embodiment.

Particle diameter (D50) of the inorganic additive is 0.1 to 10 μm in anembodiment, 0.2 to 5 μm in another embodiment, 0.3 to 3.1 μm in anotherembodiment, and 0.4 to 1.9 μm in another embodiment. The particlediameter (D50) can be measured by laser diffraction scattering methodwith Microtrac model S-3500.

The inorganic additive is 0.1 parts by weight or more in an embodiment,0.3 parts by weight or more in another embodiment, 0.6 parts by weightor more in another embodiment, 0.9 parts by weight or more in anotherembodiment against 100 parts by weight of the conductive powder. Theinorganic additive is 5.0 parts by weight or less in an embodiment, 3.8parts by weight or less in another embodiment, 2.5 parts by weight orless in another embodiment, 1.8 parts by weight or less in anotherembodiment against 100 parts by weight of the conductive powder.

The inorganic additive is 0.1 to 5 wt. % in an embodiment, 0.3 to 4.0wt. % in another embodiment, 0.5 to 2.9 wt. % in another embodiment, 0.8to 1.8 wt. % in another embodiment based on the weight of the conductivepaste.

EXAMPLES

The present invention is illustrated by, but is not limited to, thefollowing examples.

100 parts by weight of the silver powder, 0.5 parts by weight of theglass frit and 1.3 parts by weight of the inorganic additive weredispersed in an organic vehicle in a mixer and homogenized by athree-roll mill. The inorganic additive was a mixture of a Cu₂O powderand a Fe₂O₃ powder at mixing weight ratio (Cu₂O:Fe₂O₃) of 2.6:1. Theparticle diameter (D50) of the silver powder was 0.8 μm. The glass fritcompositions are shown in Table 1. The organic vehicle was a mixture of9 wt. % of an organic polymer, 87 wt. % of a solvent and 4 wt. % oforganic additives based on the weight of the organic vehicle. The pasteviscosity was about 300 Pa-s measured by Brookfield HBT with a spindle#14 at 10 rpm.

The conductive paste was screen printed on Al₂O₃ and(Zr_(0.8)Sn_(0.2))TiO₄ substrates (25 mm long, 25 mm wide, 0.6 mm thick)in a ring pattern (2.5 mm wide, 10 μm thick, 80 mm round length).Dielectric constant of the substrates were 9 for Al₂O₃ and 38 for(Zr_(0.8)Sn_(0.2))TiO₄. The electrode was formed by firing the ringpattern at peak temperature of 900° C. for 10 minutes after drying at150° C. for 10 minutes.

Next, the sheet resistivity (Rs) of the electrode was measured toconfirm the electrode had a sufficiently low resistivity. The electrodewas newly formed on the same substrate by the same method describedabove except that the electrode was a line pattern (0.5 mm wide, 100 mmlong and 10 μm thick). The resistivity was measured with a digitalmultimeter (Model 2100, Keithley Instruments, Inc.).

The results were shown in Table 2. The conductive paste comprising theglass frit comprising SiO₂, B₂O₃, Al₂O₃ and the alkaline metal oxide(Example (Ex.) 1 to 11) showed improved Q values on each testedsubstrate. It's also confirmed that the all electrodes had sufficientlylow resistivity of 2.0 mohm/sq or lower.

TABLE 1 (wt. %) Alkaline Metal Oxide Additional Metal Oxide Glass # SiO₂B₂O₃ Al₂O₃ Bi₂O₃ Li₂O Na₂O K₂O ZrO₂ TiO₂ CaO ZnO MgO CuO Fe₂O₃ Ts (° C.)A 70.2 24.4 1.0 0 0.5 0.5 1.0 2.4 0 0 0 0 0 0 804 B 69.1 24.0 1.0 0 0.50.5 1.0 0 3.9 0 0 0 0 0 797 C 66.4 23.1 0.9 0 0.5 0.5 1.0 0 7.8 0 0 0 00 789 D 70.0 24.3 1.0 0 0.5 0.5 1.0 0 0 2.8 0 0 0 0 834 E 69.1 24.0 1.00 0.5 0.5 1.0 0 0 0 4.0 0 0 0 850 F 66.3 23.0 0.9 0 0.5 0.5 0.9 0 0 07.9 0 0 0 862 G 70.5 24.5 1.0 0 0.5 0.5 1.0 0 0 0 0 2.0 0 0 840 H 69.024.0 1.0 0 0.5 0.5 1.0 0 0 0 0 4.1 0 0 853 I 69.2 24.0 1.0 0 0.5 0.5 1.00 0 0 0 0 3.9 0 834 J 69.1 24.0 1.0 0 0.5 0.5 1.0 0 0 0 0 0 0 3.9 798 K72.0 25.0 1.0 0 0.5 0.5 1.0 0 0 0 0 0 0 0 766 L 7.1 8.4 2.1 69.8 0 0 0 00 0.5 12.0 0 0 0 524

TABLE 2 (parts by weight) Com. Ex. 1 Ex. 2 Ex. 3 Ex. 4 Ex. 5 Ex. 6 Ex. 7Ex. 8 Ex. 9 Ex. 10 Ex. 11 Ex. 1 Silver powder 100 100 100 100 100 100100 100 100 100 100 100 Glass frit A B C D E F G H I J K L 0.5 0.5 0.50.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 Organic vehicle 19.5 19.5 19.5 19.519.5 19.5 19.5 19.5 19.5 19.5 19.5 19.5 Inorganic additive 1.3 1.3 1.31.3 1.3 1.3 1.3 1.3 1.3 1.3 1.3 1.3 Rs (mohm/sq.) 1.8 1.8 1.9 1.9 1.81.9 2.0 1.9 1.9 1.8 1.9 1.8 Q value on Al₂O₃ at 2910 2898 2899 2833 29142855 2891 2870 2919 2935 2880 2647 2.7 GHz Q value on 1424 1401 14141387 1388 1365 1398 1370 1415 1392 1406 1312 (Zr_(0.8)Sn_(0.2))TiO₄ at2.6 GHz

What is claimed is:
 1. A method of manufacturing a dielectric filter,comprising the steps of: (a) preparing a ceramic substrate; (b) applyinga conductive paste on the ceramic substrate, wherein the conductivepaste comprises, (i) 100 parts by weight of a conductive powder, (ii)0.1 to 10.0 parts by weight of a glass frit comprising silicon oxide,boron oxide, aluminum oxide and an alkaline metal oxide, and (iii) anorganic vehicle; and (c) firing the applied conductive paste.
 2. Themethod of claim 1, wherein at least 60 mol % of metal components of theceramic substrate are selected from the group consisting of Al, Ba, Ca,La, Mg, Mn, Nb, Nd, Ni, Pb, Sm, Sn, Sr, Ta, Ti, Zn, Zr and a mixturethereof.
 3. The method of claim 1, wherein the conductive paste isapplied on the entire surface of the ceramic substrate.
 4. The method ofclaim 1, wherein the dielectric filter is TEM (transverseelectromagnetic) mode.
 5. The method of claim 1, wherein particlediameter (D50) of the conductive powder is 0.01 to 10 μm.
 6. The methodof claim 1, wherein the glass frit comprises 30 to 85 wt. % of siliconoxide, 11 to 50 wt. % of boron oxide and 0.1 to 5.0 wt. % of aluminumoxide and 0.5 to 6 wt. % of the alkaline metal oxide based on the weightof the glass frit.
 7. The method of claim 1, wherein the alkaline metaloxide comprises lithium oxide, sodium oxide and potassium oxide.
 8. Themethod of claim 1, wherein the glass frit further comprises anadditional metal oxide selected from the group consisting of zirconiumdioxide, titanium oxide, calcium oxide, zinc oxide, magnesium oxide,copper oxide, iron oxide and a combination thereof.
 9. The method ofclaim 8, wherein the additional metal oxide is selected from the groupconsisting of zirconium oxide, titanium oxide, zinc oxide, copper oxide,iron oxide and a combination thereof.
 10. The method of claim 8, whereinthe additional metal oxide is 0.5 to 20 wt. % based on the weight of theglass frit.
 11. The method of claim 1, wherein the firing temperature instep (c) is 600 to 1100° C.
 12. A conductive paste to form an electrodeof dielectric filter, wherein the conductive paste comprises: (i) 100parts by weight of a conductive powder, (ii) 0.1 to 10.0 parts by weightof a glass frit comprising silicon oxide, boron oxide, aluminum oxideand an alkaline metal oxide, and (iii) an organic vehicle.
 13. Theconductive paste of claim 12, wherein the conductive powder is a metalpowder with electrical conductivity of 7.00×10⁶ Siemens (S)/m or higherat 293 Kelvin.
 14. The conductive paste of claim 12, wherein the glassfrit comprises 30 to 85 wt. % of silicon oxide, 11 to 50 wt. % of boronoxide and 0.1 to 5.0 wt. % of aluminum oxide and 0.5 to 6 wt. % of thealkaline metal oxide based on the weight of the glass frit.
 15. Theconductive paste of claim 12, wherein the alkaline metal oxide compriseslithium oxide, sodium oxide and potassium oxide.
 16. The conductivepaste of claim 12, wherein the glass frit further comprises anadditional metal oxide selected from the group consisting of zirconiumdioxide, titanium oxide, calcium oxide, zinc oxide, magnesium oxide,copper oxide, iron oxide and a combination thereof.
 17. The conductivepaste of claim 16, wherein the additional metal oxide is selected fromthe group consisting of zirconium oxide, titanium oxide, zinc oxide,copper oxide, iron oxide and a combination thereof.
 18. The conductivepaste of claim 16, wherein the additional metal oxide is 0.5 to 20 wt. %based on the weight of the glass frit.
 19. A dielectric filtercomprising a ceramic substrate and an electrode on the ceramicsubstrate, the electrode comprises (i) 100 parts by weight of aconductive powder, and (ii) 0.1 to 10.0 parts by weight of a glass fritcomprising silicon oxide, boron oxide, aluminum oxide and an alkalinemetal oxide.
 20. The dielectric filter, wherein the dielectric filter isTEM (transverse electromagnetic) mode.